Huffman编码

#include "stdafx.h"
#include <cstdio>
#include <cstdlib>
#include <cstring>
#define MIN 1000


typedef struct{
    unsigned int weight;
    unsigned int parent,lchild,rchild;
}HTNode, *HuffmanTree;

typedef char ** HuffmanCode;

void Select(HuffmanTree HT,int i, int &s1, int &s2)
{
    int j;
    int min=MIN;
    for(j=1;j<i;j++)
    {
        if(HT[j].weight<=min&&HT[j].parent==0)
        {    min=HT[j].weight;
            s1=j;
        }
    }
    
    min=MIN;
    for(j=1;j<i;j++)
    {
        if((HT[j].weight<=min)&&(j!=s1)&&HT[j].parent==0)
        {
            min=HT[j].weight;
            s2=j;
        }
    }
}

void HuffmanCoding(HuffmanTree &HT,HuffmanCode &HC, int *w, int n)
{
    
    int m,i,s1=1,s2=1,f,c,start;
    char *cd;
    HuffmanTree p;
    if(n<=1) return;
    m=2*n-1;
    HT=(HuffmanTree)malloc((m+1)*sizeof(HTNode));   //0号单元未用
    for(p=HT+1,i=1;i<=n;++i,++p,++w)
        {
            //*p={*w,0,0,0};
            p->weight=*w;       //******************这里注意赋值的格式
            (*p).parent=0;      //******************如果采用这种格式是错误的：  *p.parent=0
            (*p).lchild=0;
            (*p).rchild=0;
            printf("the weight of HT[%d] is %d\n",i,HT[i].weight);
        }            
    for(;i<=m;++i)
        {
            //*p={0,0,0,0};
            (*p).weight=*w;
            (*p).parent=0;
            (*p).lchild=0;
            (*p).rchild=0;
        }
        
    for(i=n+1;i<=m;++i)
    {
        Select(HT,i-1,s1,s2);
        printf("s1=%d,s2=%d\n",s1,s2);
        HT[s1].parent=i;
        HT[s2].parent=i;
        HT[i].lchild=s1;
        HT[i].rchild=s2;
        HT[i].weight=HT[s1].weight+HT[s2].weight;
    }
    
    HC=(HuffmanCode)malloc((n+1)*sizeof(char*));
    cd=(char*)malloc(n*sizeof(char));            //这里开辟一个较大的空间，因为长度不可能超过n
    cd[n-1]='\0';
    for(i=1;i<=n;++i)
    {
        start=n-1;
        for(c=i,f=HT[i].parent;f!=0;c=f,f=HT[f].parent)
            if(HT[f].lchild==c)
                cd[--start]='0';
            else
                cd[--start]='1';
        HC[i]=(char*)malloc((n-start)*sizeof(char));         //这里开辟编码长度的空间
        strcpy(HC[i],&cd[start]);                    //巧妙之处：这里从cd数组的中间已经编码的元素开始拷贝
    }
    free(cd);
}
 

int _tmain(int argc, _TCHAR* argv[])
{
 HuffmanTree HT;
 HuffmanCode HC;
 int w[5]={1,2,3,4,5};
 int n=5,i;
 HuffmanCoding(HT,HC,w,n);
 for(i=1;i<=n;i++)
  printf("the i node coding is %s\n",HC[i]);
 while(1);
 return 0;
}